1. Technical Field
Embodiments of the present disclosure relate generally to video decoders, and more specifically to pixel retrieval for frame reconstruction in a video decoder.
2. Related Art
Frame reconstruction refers to operations performed to reconstruct compressed and encoded image frames in a video decoder. Image frames (also referred to as image frames) may be encoded using intra-frame, inter-frame or a combination of intra and inter-frame encoding techniques, such as for example, specified by the H.264 standard. The H.264 is described in further detail in ITU-T Recommendation H.264—“SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS, Infrastructure of audiovisual services—Coding of moving video, Advanced video coding for generic audiovisual services”, available from TELECOMMUNICATION STANDARDIZATION SECTOR of ITU. When inter-frame encoded frames (P-frames and B-frames) are to be reconstructed, an operation termed motion compensation is performed. The motion compensation operation involves determining, for a macro-block (or for portions termed partitions of a macro-block), a best-matching macro-block (or partition) in a previous or future frame (referred to as a reference frame).
Pixel values representing macro-blocks (or portions thereof) in an image frame are often stored in an external memory. External memory as referred to herein generally refers to memory that is physically located outside of a circuit portion performing the motion compensation. For example, when a circuit portion performing the motion compensation operation is contained in an integrated circuit (IC), an off-chip memory component may be referred to as an external memory. To perform motion compensation, pixel values of the best-matching macro-block (or partition) in a reference frame may need to be fetched from such external memory and stored for processing in an on-chip or internal memory. The time spent in performing such external memory fetches may need to be minimized or at least predictable in many operating environments. In general, pixel retrieval operations from an external memory to an internal memory of a video decoder may need to be made efficient.